A Si3N4 PIC for optically controlled 2D radio beamforming in satellite communications

We designed and fabricated a Silicon Nitride (Si₃N₄) photonic integrated circuit targeting wideband two-dimensional radio beamforming from 20-40 GHz for satellite communications. Continuous true time delay tunability is achieved by using thermo-optic phase shifters in a 2-port optical ring resonator. Scanning angles up to 20° and true time delay bandwidth up to 14 GHz are realized while tuning into the anti-resonance response of the ring resonator. An optical side-band filter using a double-ring loaded Mach-Zehnder interferometer with an FSR of 0.48 nm is designed for a single side band operation. The fabricated photonic integrated circuit is a 4-input / 4-output beamformer for a 2-by-2 focal plane antenna array. It is the first PIC beamformer circuit on Si₃N₄ designed for operation in the 20-40 GHz band.